1. Field of the Invention
The present invention relates to explosives that can sever a target such as the canopy of an airplane or the skin of a missile.
2. Description of Related Art
Most military aircraft are constructed with an ejection seat that allows the pilot to escape the vehicle while in flight. Ejection seats typically have rockets which propel the pilot through the canopy of the plane. It has been found that the impact of the seat and pilot on the canopy, can cause serious injury to the head and spine of the pilot. To correct this problem, an explosive charge is incorporated into the cockpit to shatter or sever the canopy, before the seat and pilot reach the transparent member. Many present day aircraft typically have mild detonating cord (MDC) attached directly to the canopy, that shatters the window when detonated. The cord is usually connected to the seat through a timer that delays the ignition of the seat rockets until the cord has detonated, insuring that the canopy is ruptured before the seat reaches the top of the cockpit.
The explosive power of MDC is somewhat limited because of the large impact area of the charge, which tends to distribute the load of the explosion and reduce the force therein. It has been found that most common types of MDC do not provide a sufficient blast force to penetrate some of the thicker and stronger canopies of present day design. One solution is to increase the blast energy of the cord, but the explosion of such a device can be harmful to the pilot.
Another type of explosive typically used to shatter canopies is a linear shaped charge (LSC). A LSC has a retainer that houses a charge which is in close proximity to the canopy. Upon detonation, the charge produces a high energy jet that cuts the canopy. The charge must be spaced from the target so that the jet can develop. Unfortunately the space between the charge and the target dissipates a large amount of the energy produced by the detonated charge. Additionally, it has been found that exact dimensional requirements for the charge and spacing are necessary to obtain an effective explosive. Another associated problem with the space between the charge and the target, is the contamination and degradation of the charge from exposure to the environment. When the charge is no longer functional, it must be replaced, a time consuming procedure that creates added down time for the airplane. It would therefore be desirable to have an explosive charge which improves the severance efficiency of present charges, while being inexpensive to produce and easy to maintain.